My guess would be that since the 1M is already basically factory modded you'll get less modders than you would with a regular One series. I basically bought my 135 with intentions to mod. I'd rather have started with a 1M but that was not an option in 2008.
If I had a 1M I'd upgrade the diverter valves and chargepipe before increasing boost levels (before a tune). It might just be considered overkill if you are still running factory boost levels.
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